I decided to tackle building my own LEGO Mindstorms NXT 'Beer & Soft Drink Bottle Opener'.
The task turned out to be somewhat more difficult than I envisaged. The most difficult part by far was the Gripper Mechanisms, as they both had to securely hold the Bottle and it's cap in such a manor that allowed them to be unscrewed. But after some trial and error, I eventually won!

About this creation

Multi-views of the LEGO Mindstorms NXT 'Drink Bottle Opener's' are shown below.. For ease of viewing the important modules that make up the 'NXT Drink Bottle Opener', I have chosen to us CAD images. As I build mainly with Black, it makes photographing detail a bit difficult. I also couldn't be bothered dusting off and setting up my Macro Camera Equipment I normally use. But I think you will agree that the CAD is a better choice.

Multi-views of the NXT Beer & Soft Drink Bottle Opener

A single NXT Brick controls the 'Drink Bottle Opener' Mechanism. It us 5x NXT Motors, 2x RCX Type Touch (+1 NXT Touch Sensor for Trigger) Sensors. To control the two extra NXT motor, I have used a Mindsensor Multiplexer for NXT Motors (NXTMMX-v2) . I must get around to purchasing a second NXTMMX, as they easy and reliable to use. The Motor requires an additional 9 Volt power Supply. Hence the 9 Volt Battery Box pictured. As this is a stationary Robot, I prefer to use a 'Regulated' 9 Volt Power Supply for all its energy requirements. This method is also great during programming and debugging the Robot. Saves a lot of battery swapping and charging time.

LEGO Mindstorms NXT Bottle Opener's Conveyor System

NXT Drink Bottle Opener Loading mechanism consists of the Conveyor System that carries the Drink Bottle to the Bottle Clamp Claw module ready for uncapping. This chain of events is triggered via a NXT Touch Sensor which is used to start the NXT Drink Bottle Opener.

LEGO Mindstorms NXT Bottle Opener's Bottle Gripper

Drink Bottle Opener's Conveyor module is used to transfer the Drink Bottle to the Claw Mechanism ready for opening. The Mindsensor MotorMux is used to control the attached NXT Motor.

LEGO Mindstorms NXT Bottle Opener's Piers with Rack System

A 8-Tooth gears attached to the NXT Motor drives a 24-Tooth gear, resulting a 1:3 reduction in the speed of the Conveyor Belt. Drink Bottle Opener's Gear Racked Pier is what the 'Control & Uncap Mechanism' slide up and down into position with. (Note the CAD is a abbreviated version of the Piers I used).

NXT Bottle Opener's Control Centre & Lift Mechanism

Once the Bottle is loaded into the NXT Drink Bottle Opener, the top assembly is lowered down so the 'Cap Gripper Mechanism' is touching the top of the bottle cap. Slowly the jaws of the Cap Gripper is closed around the bottle cap ready for unscrewing. Now that the 'Cap Gripper Mechanism' has gip of the bottle cap, the 'Cap Gripper Mechanism' is rotated six times to unscrew the bottle cap. The 'Cap Gripper Mechanism' jaws are loosened and the mechanism is lifted above the the cap so the bottle can be removed via the 'Conveyor Belt' ready for the user to drink.

LEGO Mindstorms NXT Bottle Opener's Bottle Cap Gripper

Key to the success of the 'Cap Gripper Mechanism' is the 'Adhesive Rubber Feet' used too fix to objects to avoid the from scratching surfaces. I purchased a pack of 16 for around $1 a few years ago to attach to the black melamine board the large LEGO Base Plate is attached to. One 'Adhesive Rubber Foot' is attached to each of the Yellow Jaws, which Grip the Bottle Cap, as shown in the CAD drawings. They feet grip extremely well to LEGO, and with a little difficulty can be remove from the LEGO Parts. When removed they leave no sticky residue and can be reused several times, as I discovered whilst going through the prototyping stages of Gripper's development.

LEGO Mindstorms NXT Bottle Opener's Bottle Cap Gripper Pads

The 'Bottle Gripper' consists mainly as a gear train. It uses a clutch at the primary stage of the gearing to avoid damage like shown at the end of the project. The Clutch drive a second down gearing before the output goes to a dual out put Worm Drive. The worm directly drives two 8-Tooth Gear on each side of the worm. The 8-Tooth gears in turn drive a 24-Tooth gear on each side held in place via a set of Technics 'Triangles'. The output from 24-Tooth gear's shafts drive a train of three 16-Tooth gears on each side, with the final output driving a set of CAMs. These Cams push the Gripper Arm inwards, gripping the bottle. The 'Bottle Gripper' is driven via a NXT Motor controlled via the Mindsensor Multiplexer for NXT Motors (NXTMMX-v2).

LEGO Mindstorms NXT Bottle Opener's Bottle Cap Gripper

The 'Bottle Cap Gripper' relies on high torque to produces the forces required to grip a bottle cap for unscrewing. Prior to entering the Worm Gears, the NXT Motor speed/torque is reduced by a factor of 1:15. The ratio is further geared down by a factor of 1:3 before moving the CAM that pushes the YELLOW 'Bottle Cap Gripper' arms. The total Gear Reduction used to drive the Gripper Arm Cams is 1:45. This produces very high torque, but with the trade off producing considerable speed reduction.

LEGO Mindstorms NXT Bottle Opener's Bottle Cap Gripper

Directly driving the gripper arms can't successfully be used without a barrow load of backup 16-Tooth Gears. The 16-Tooth Gears fail catastrophically (See Conclusion). Using the CAMs solves this issue. A 'White Technic Clutch' is used in the primary part of the drive-line to help protect the gears.

LEGO Mindstorms NXT Bottle Opener's Bottle Cap Gripper

Drink Bottle Top Lifting Mechanism raises the 'Bottle Cap Jaws & Unscrewing Modules. The mechanism lifts and lowers the 'Bottle Cap Gripper' into place. The mechanism moves on two piers 'Gear Racks'. The Mechanism also carries the Bottle Cap Gripper and Bottle Cap unscrewing NXT Motor , as well as the NXT Motor that propels it up and down the Gear Rack. The NXT Brick also is attached to this mechanism.

LEGO Mindstorms NXT Bottle Opener

By far the hardest part of the Bottle Opener build, was gripping the bottle and cap in a manor that allowed the Cap to be successfully removed. Getting the 'Drink Bottle Opener' to work successfully needed a large amounts of torque in order to clamp the Bottle Body and Cap.I found uncapping "Beer Stubbies" with their crinkle edged caps a far easier challenge when compared to the 'Smooth Edged' "Soft Drink Bottles". - - When I moved onto the challenge of Soft Drink Bottle Caps, I started to see a lot of LEGO Parts flying across the room. During my prototyping I had a few Technics Shafts ending up as Cork-screws and a 16-tooth Gear redesign. In one piece most of the time. I note that a 16-Tooth Gear at high velocity hurts somewhat when they collide with your head. Leaving their imprint as a warning!

LEGO Mindstorms NXT Bottle Opener Produced Gear Failure

The Software to drive the 'Drink Bottle Opener' Mechanisms is written in RobotC.

Despite a lot of initial frustration, the Sun rise surprising me twice, and a lot of hair pulling. It was worth the building challenge.I hope you have enjoyed discovering this project of mine. Please feel free to take full advantage of the supplied LEGO Digital Designer CAD files.

Download LEGO Digital Designer CAD Files:

For full project details, including more information, video and Code examples: "www.rjmcnamara.com".